Advanced Compiler Design
CSE 231
Instructor: Sorin Lerner
Let’s look at a compiler
if (…) { x := …;} else { y := …;}…;
ExecCompilerParserCodeGen
Compiler
Optimizer
ParserParserCodeCodeGenGen
CompilerCompiler
ParserCodeGen
Compiler
Let’s look at a compiler
Optimizer
Advanced Optimizer Design
CSE 231
Instructor: Sorin Lerner
What does an optimizer do?
1.Compute information about a program2.Use that information to perform program
transformations (with the goal of improving some metric, e.g. performance)
ParserParserCodeCodeGenGen
CompilerCompiler
Optimizer
What do these tools have in common?
• Bug finders
• Program verifiers
• Code refactoring tools
• Garbage collectors
• Runtime monitoring system
• And… optimizers
What do these tools have in common?
• Bug finders
• Program verifiers
• Code refactoring tools
• Garbage collectors
• Runtime monitoring system
• And… optimizers
They all analyze and transform programsWe will learn about the techniques underlying all these tools
Program Analyses, Transformations,and Applications
CSE 231
Instructor: Sorin Lerner
Course goals
• Understand basic techniques– cornerstone of a variety of program analysis tools– useful no matter what your future path
• Get a feel for compiler research/implementation– useful if you don’t have a research area picked– also useful if you have a research area picked
Course topics
• Representing programs
• Analyzing and transforming programs
• Applications of these techniques
Course topics (more details)
• Representations– Abstract Syntax Tree– Control Flow Graph– Dataflow Graph– Static Single Assignment– Control Dependence Graph– Program Dependence Graph– Call Graph
Course topics (more details)
• Analysis/Transformation Algorithms– Dataflow Analysis– Interprocedural analysis – Pointer analysis– Rule-based analyses and transformations– Constraint-based analysis
Course topics (more details)
• Applications– Scalar optimizations– Loop optimizations– Object oriented optimizations– Program verification– Bug finding
Course pre-requisites
• No compilers background necessary
• No familiarity with lattices– I will review what is necessary in class
• Familiarity with functional/OO programming– Optimization techniques for these kinds of languages
• Standard ugrad cs curriculum likely enough– Talk to me if you’re concerned
Course work
• In-class midterm (30%)
• Take-home final (30%)
• Course project (35%)
• Class readings (5%)
Course project
• Goal of the project– Get some hands on experience with compilers
and/or Get a feel for what research is like in PL
• Three kinds of projects:– research-y: explore some interesting ideas and try
them out– implementation-y: pick some existing idea out there,
and implement it – paper-y: read 10 good papers on a topic, and write a
report summarizing and integrating
Course project
• Groups of 3 (make groups by this Friday)
• Pick something to advance your personal enrichment goals
• Eg: Pick something related to your research, something that you want to learn about
• Milestones– Project proposal (due end of week 2)– Mid-point status report (5 weeks in)– Final presentation/written report (end of quarter)
Readings
• Paper readings throughout the quarter
• Seminal papers and state of the art
• Will give you a feel for what research looks like
Administrative info
• Class web page is up– http://cseweb.ucsd.edu/classes/sp15/cse231-a/– (or Google “Sorin Lerner”, follow “Teaching Now”)– Will post lectures, readings, project info, etc.
• Piazza link on web page– Use for questions, answers– Especially LLVM/project Q&A
Academic Integrity
• Governed by Policy on Integrity of Scholarship (http://senate.ucsd.edu/Operating-Procedures/Senate-Manual/Appendices/2)
• Allegations are handled by Academic Integrity Office (https://students.ucsd.edu/academics/academic-integrity)
• Course penalty for any cheating in 231 will be a failing grade for the entire class
• Cheaters may be subsect to additional administrative sanctions
Questions?
Program Analyzer Issues (discuss)
ProgramAnalyzerInput Output
Program Analyzer Issues (discuss)
ProgramAnalyzerInput Output
Program Analyzer Issues (discuss)
ProgramAnalyzerInput Output
Input issues
• Input is a program, but…
• What language is the program written in?– imperative vs. functional vs. object-oriented? maybe
even declarative?– what pointer model does the language use?– reflection, exceptions, continuations?– type system trusted or not?– one often analyzes an intermediate language... how
does one design such a language?
Instructor’s discussion notes
ProgramAnalyzerInput Output
Input issues
• How much of the program do we see?– all?– one file at a time?– one library at a time?– reflection…
• Any additional inputs?– any human help?– profile info?
Instructor’s discussion notes
ProgramAnalyzerInput Output
Analysis issues
• Analysis/compilation model– Separate compilation/analysis
• quick, but no opportunities for interprocedural analysis
– Link-time• allows interprocedural and whole program analysis• but what about shared precompiled libraries?• and what about compile-time?
– Run-time• best optimization/analysis potential (can even use run-time state as
additional information)• can handle run-time extensions to the program• but severe pressure to limit compilation time
– Selective run-time compilation• choose what part of compilation to delay until run-time• can balance compile-time/benefit tradeoffs
Instructor’s discussion notes
ProgramAnalyzerInput Output
Analysis issues
• Does running-time matter?– for use in IDE? – or in overnight compile?
Instructor’s discussion notes
ProgramAnalyzerInput Output
Output issues
• Form of output varies widely, depending on analysis– alias information– constantness information– loop terminates/does not terminate
• Correctness of analysis results– depends on what the results are used for– are we attempting to design algorithms for solving
undecidable problems?– notion of approximation– statistical output
Instructor’s discussion notes
ProgramAnalyzerInput Output
Program Transformation Issues (discuss)
ProgramTransformerInput Output
Input issues
• A program, and …
• Program analysis results
• Profile info?
• Environment: # of CPUs, # of cores/CPU, cache size, etc.
• Anything else?
Instructor’s discussion notes
ProgramTransformerInput Output
Transformation issues
• What is profitable?
• What order to perform transformations?
• What happens to the program representation?
• What happens to the computed information? For example alias information? Need to recompute?
Instructor’s discussion notes
ProgramTransformerInput Output
Output issues
• Output in same IL as input?
• Should the output program behave the same way as the input program?
Instructor’s discussion notes
ProgramTransformerInput Output
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